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All Tied Up In Knots

In this activity, students learn a topological trick with a rope.

Topology is the mathematical study of shapes and spaces. It involves looking at the shapes that result through stretching, transforming, deforming, folding and twisting. Tearing, on the other hand, is not allowed!

Scientists often have to think creatively to solve problems or figure out how something works.

This activity will get your students thinking with their hands!

Objectives

  • Explain the importance of observation when doing science.

Materials

  • Per Class or Group:
    2 or 3 lengths of rope (1m+)

What To Do

Preparation:

  1. Set up the room so that there is enough space for volunteers to be clearly seen by the other students.

Instructions:

  1. Ask for 3 volunteers and have them tie a simple overhand knot (the first step in tying your shoe) in the middle of their ropes.
  2. Now have them attempt to do the same thing again, except this time, they can’t let go of their rope in any way once they pick it up. (Passing it from hand to hand is the same as letting go.)    Tip: They’ll have trouble with this!
  3. Ask a few other students to come up with a solution or try it themselves before you reveal the secret.
  4. Demonstrate the secret. It’s easy! Simply fold your arms before you pick up the rope. All you need to do is to straighten out your arms while holding the rope and the knot will tie itself!Tip: Arms must be folded with one hand passing under the opposite arm like this: